1. Field of the Invention
The present invention relates to systems, methods, and computer programs for detecting wafer location, and more particularly, systems, methods and computer programs for detecting wafer location using optical sensors on wafer handling robots, and if the wafer is present in a correct orientation before and after the end effector contacts a wafer.
2. Description of the Related Art
An end effector is a device or tool that's connected to the end of a robot arm. The end effector is the part of the robot that interacts with the environment. In semiconductor manufacturing, some end effectors are employed to transport semiconductor wafers between different locations, such as transporting wafers from an alignment station to an etching station, or between wafer storage and tools.
When transporting semiconductor wafers via a robotic arm end effector, various sensors can be built into the end effector structure. The sensors can detect if the wafer has slipped, shifted, or if the wafer has been properly loaded in the end effector and is in a safe transfer location. Prior to transporting wafers via robotic arm end effector, the wafer's location in a holder maybe determined with additional sensors built into the end effector to “map” wafer location. In some end effectors, two separate sensors with supporting electronics and power consumption are typically placed in the end effector to locate and transport safely a wafer via the robotic arm. Thus, an end effector may have to perform two separate detection functions: presence and mapping.
It is in this context that embodiments of the invention arise.